Sulfur Passivation of GaSb(100) Surfaces: Comparison of Aqueous and Alcoholic Sulfide Solutions Using Synchrotron Radiation Photoemission Spectroscopy

Abstract

In an attempt to rationalize empirically developed GaSb device optimization using alcoholic versus aqueous sulfide solutions, synchrotron radiation photoemission spectroscopy (SXPS) has been applied to study the chemical composition and the electronic properties of the GaSb(100) surface treated with ammonium sulfide dissolved in water versus 2-propanol. In addition the initial native oxide layer on GaSb(100) surface has been analyzed in detail. The variation of the solvent leads to variations in the chemical composition and electronic structure of the final sulfide layers. In the deeper parts of the passivation layers, the Ga/Sb atomic ratio is around 1 for 2-propanol and 2 for aqueous solution. Right at the surface it is 0.15 and 0.4, respectively. Valence band maximum and core levels of the sulfide layers are found at 0.26 and 0.4 eV higher binding energies using 2-propanol versus aqueous solution. Almost no oxygen is left on the surface treated using ammonium sulfide in 2-propanol, while with use of aqueous ammonium sulfide solution, inclusions of Ga 2 O 3 are found. The carbon contamination is reduced 4 times using alcoholic, while it is increased by a factor of 1.25 with aqueous solution.

Surfactant-assisted chemical vapour deposition of high-performance small-diameter GaSb nanowires

“…In the present study, we explore the use of surfactant (sulfur) for the CVD growth of NWs in order to achieve very thin GaSb NWs with the diameter down to 20 nm. In contrast to the surfactant effect typically reported in the liquid phase [22][23][24][25][26][27] (for example, solvothermal and hydrothermal) and thin-film technologies 28 , the sulfur atoms, commonly used for the surface passivation of III-V semiconductors [29][30][31][32] , are contributed to form S-Sb bonds on the as-grown NW surface, effectively stabilizing the sidewalls and thus minimizing the unintentional radial growth. Importantly, the obtained NWs are highly stoichiometric, single-crystalline with a smooth surface and very uniform in diameter without any tapering.…”

Superior electronic passivation of n-GaP(100) surface using alcoholic as compared to aqueous ammonium sulfide solution: Wet processing studied with synchrotron photoelectron spectroscopy

“…b). The increase in carbon contamination after treatment with the aqueous solution of ammonium sulfide and decrease after treatment with ammonium sulfide in 2‐propanol was observed before on the GaSb(100) surface .…”

“…This result is counter‐intuitive since e.g. in the case of the GaSb(100) surface the solution of ammonium sulfide in 2‐propanol removes the native oxide completely, whereas after treatment with aqueous ammonium sulfide solution some native oxide remains on the surface . On the other hand, the 2‐propanol solution reduces the carbon contamination considerably, whereas the aqueous solution increases the carbon contamination (Fig.…”

Bismuth Oxysulfide Photoelectrodes with Giant Incident Photon‐to‐Current Conversion Efficiency: Chemical Stability in Aqueous Solutions

“…In the case of significantly shorter soaking times (minutes), both XRD and Raman spectra do not demonstrate the formation of Bi 2 S 3 phase. Nevertheless, one can expect that formation of S‐terminated surface could take place under these conditions due to both ion exchange in thin near‐surface layers and chemical absorption of S 2− anions ,,…”